In the Linux kernel, the following vulnerability has been resolved:
net: thunderbolt: Fix frags[] overflow by bounding frame_count
tbnet_poll() assembles a multi-frame ThunderboltIP packet into one skb. The
first frame goes into the skb linear area and every further frame is added as
a page fragment.
skb_add_rx_frag(skb, skb_shinfo(skb)->nr_frags,
page, hdr_size, frame_size,
TBNET_RX_PAGE_SIZE – hdr_size);
A packet of frame_count frames therefore ends up with frame_count – 1
fragments. tbnet_check_frame() only bounds the peer supplied frame_count to
TBNET_RING_SIZE / 4 (64), which is far above MAX_SKB_FRAGS (17 by default). A
peer that sends a packet of 19 or more small frames pushes nr_frags past
MAX_SKB_FRAGS, so skb_add_rx_frag() writes past skb_shinfo()->frags[] and
corrupts memory after the shared info.
Tighten the start of packet bound to MAX_SKB_FRAGS + 1 so a packet can never
produce more fragments than frags[] can hold. This matches the recent skb
frags overflow fixes in other receive paths, for example f0813bcd2d9d (“net:
wwan: t7xx: fix potential skb->frags overflow in RX path”) and 600dc40554dc
(“net: usb: cdc-phonet: fix skb frags[] overflow in rx_complete()”).
